Quantum mechanics typically influences the behavior of small particles, but at extremely low temperatures, quantum effects can manifest on a larger scale. For instance, helium can become a superfluid, exhibiting unique properties like flowing without energy loss and even climbing the walls of a container.
Researchers, led by physicist Samuli Autti of Lancaster University in the UK, have now provided insight into what it would be like to touch and interact with this quantum system, addressing a longstanding challenge at the intersection of quantum and classical physics. This breakthrough comes after a century of unanswered questions in quantum physics.
What Does Superfluid Helium Feels Like?
An experiment has offered insights into the sensation of touching a quantum superfluid. Scientists submerged a specially designed finger-sized probe into helium-3, an isotope of helium, cooled to just above absolute zero and observed its physical properties. It's the first time anyone has gained an understanding of how it feels to interact with the quantum realm.
The research, published in the journal Nature Communications, provides a unique perspective on quantum physics. Their study involved superfluid helium-3, a substance that behaves like a fluid with no viscosity or friction when cooled to extremely low temperatures.
Two isotopes of helium can form superfluids, helium-4 and helium-3. When helium-4 is chilled to near absolute zero, its bosons slow down, allowing them to overlap into a high-density cluster of atoms that effectively act as a single super-atom.
On the other hand, Helium-3 is composed of fermions, particles with distinct spins compared to bosons. When it's cooled below a certain temperature, fermions form what's known as Cooper pairs, composed of two fermions that behave like a composite boson. These Cooper pairs display superfluid behavior.
Autti and his team have been studying helium-3 fermionic superfluid and developed a probe that could interact with the superfluid without breaking Cooper pairs or disrupting its flow.
Their findings revealed a peculiar behavior in which the superfluid's surface creates an independent two-dimensional layer that dissipates heat away from the probe. Beneath this surface layer, the superfluid is almost vacuum-like and lacks any discernible tactile sensation.
Unveiling a Two-Dimensional World in Quantum Superfluids
The experiment revealed that only the two-dimensional surface layer interacts with the probe, and accessing the bulk of the superfluid necessitates a substantial burst of energy. The primary determination of the superfluid's thermomechanical properties is attributed to this two-dimensional layer, while the bulk remains inert.
In practical terms, if you could insert your finger into this quantum superfluid, it would feel two-dimensional, with heat coursing through a two-dimensional subsystem along the bulk's edges, akin to the sensation along your finger, as Autti explained. This revised understanding of superfluid helium-3 has profound implications for scientists and the comprehension of quantum physics.
The research demonstrated that even though superfluid Helium-3 exists in three dimensions, it behaves thermomechanically as if it were two-dimensional.
Dr. Autti elaborated on how this discovery redefines our understanding of superfluid helium-3. This versatile macroscopic quantum system has far-reaching effects on various fields not directly linked to it, such as research related to the Higgs mechanism, cosmological theories, and intriguing phenomena like time crystals.
The researchers highlight that these research pathways hold the potential to revolutionize our comprehension of this versatile macroscopic quantum system.
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